1. Field of the Invention
The present invention relates to a method of cleaning a semiconductor wafer, and more particularly, to a method for removing ink from the surface of a semiconductor wafer.
2. Description of the Prior Art
In integrated circuit industry, in order to make active devices on a semiconductor die function properly, ceramic or plastic packaging material is typically used to wrap and protect the semiconductor die. Before a wafer is sent for package, certain electrical property tests are performed first by a wafer manufacturer in order to ensure the quality of the wafer. But since the wafer manufacturer and the wafer packaging company are usually not located at the same factory, the wafer manufacturer usually uses ink to mark each defective die of a wafer so as to distinguish good dies from bad dies of each wafer, and the wafer packaging companies will only package good dies when they receive such inked wafers.
The inking process is usually performed in an automatic testing procedure in the present semiconductor industry. The automatic testing procedure uses a testing program installed in a control unit to decide which die fails the electrical test and then uses ink to mark it. However, the testing machine used in such automatic testing procedure may sometimes become inaccurate or the testing program may use wrong testing parameters so that the marks inked by the testing machine are totally wrong. For example, the ink head may deviate from its normal position and marks on wrong dies.
When such problems occur, the ink on the surface of the wafer has to be removed. Presently the ink on such a wafer is manually washed off using sponge and acetone. The acetone is used as a cleaning solution to dissolve the ink on the surface of a wafer and the sponge is used to manually scrub off the dissolved ink from the surface of the wafer. A lot of cleaning solution is wasted in such process because the operator has to use the solution to flush the surface of the wafer continually. Besides, such process is very time-consuming and unpleasant to the operator because of the exposure to the acetone. Its efficiency is very low and the manual force exerted to the surface of the wafer may easily cause serious damage to the wafer.
It is therefore a primary objective of the claimed invention to provide a cleaning method to remove ink from the surface of a semiconductor wafer so as to solve the above-mentioned problems.
According to the claimed invention, the cleaning method includes securing the wafer to a spin chuck, using a first cleaning station to submerge the spinning wafer into an N-Methyl-Pyrolidone (NMP) solution, using a second cleaning station to spray a cleaning solution onto the surface of the spinning wafer, and using a drying station to blowing gas onto the surface of the spinning wafer to remove residue from the surface of the wafer.
It is an advantage of the present invention that the present invention provides an automatic cleaning procedure to perform the ink cleaning process. The manpower can be saved and wastes of cleaning solutions can also be reduced. Furthermore, the surface of each wafer can be cleaned in a much safer manner.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.